尿液中不同价态硒的吸附溶出伏安法测定

本文研究了在二溴代苤硒脑生成条件下Se(-Ⅱ、0)、Se(Ⅳ)、Se(Ⅵ)等不同价态硒的稳定性及其转化条件,确定了用二溴代苤硒脑体系的吸附溶出伏安法测定尿液中不同价态硒的方法.结果表明,在1.5mol/L HCl介质中,Se(Ⅳ)与二溴代邻苯二胺定量生成苤硒脑,可用吸附溶出伏安法直接测定Se(Ⅳ).HNO_3-HClO_4消化样品时,Se(-Ⅱ、0)定量转化为Se(Ⅳ),此时Se(Ⅳ)、Se(Ⅵ)价态稳定.而HNO_3-HClO_4消化样品后用3mol/L HCl将Se(Ⅵ)还原为Se(Ⅳ)后可测得总硒.故利用不同的样品处理方法所得结果差减后,测定Se(-Ⅱ、0)、Se(Ⅳ)和Se(Ⅵ)含量.本文方法用于尿液样品分析,尿液中硒的主要价态为以Se(-Ⅱ)形式存在的有机硒,无机态Se(Ⅳ)、Se(Ⅵ)的含量甚微.

Speciation of Selenium in Urine by Adsorptive Stripping Voltammetric Method

The stabilities of different species of selenium Se(-II,0), Se(IV) and Se(VI) and their transformation conditions were studies under the conditions of the formation of 4,6-dibromopiase-lenole (DB-PIS). The experimental conditions for the adsorptive stripping voltammetric determination of Se (-11,0), Se (IV) and Se (VI) in urine were thus established. Results show that in the solution of 1.5mol/L HCI, Se (IV) reacts quantitatively with DBDA resulting in the for- mation of DB-PIS and therefore Se (IV) can be determined directly by adsorptive stripping voltammetry. When the sample is digested by HNO3-HClO4, Se (-II,0) is trasformed into Se (IV), while Se (IV) and Se (VI) are both stable. Se (VI) in the sample can be reduced into Se (IV) in 3mol/L HC1 and the total selenium in the sample can thus be determined. By the difference between the results obtained from under different pretreatment conditions, Se (-II, 0), Se (IV) and Se (VI) can be determined, respectively. The method was used in the speciation analysis of selenium in urine sample. Results show that the dominant apecies of Se in urine was organic Se (-II), while Se (IV) and Se (VI) in inorganic states were of less importance.